1. Field of the Invention
The invention described herein relates to communications processing, and in particular relates to dynamic control and processing of data in the physical layer and media access control processing.
2. Background Art
In point-to-multipoint communications systems such as those operating under a version of the Data Over Cable Service Interface Specification (DOCSIS), communications that are sent from user equipment to a central controller are processed through a layered protocol stack. An example of such user equipment is a cable modem; an example of a central controller is a cable modem termination system (CMTS). Processing at a CMTS includes physical layer (PHY) processing and media access control layer (MAC) processing.
In current systems, bursts are received at a CMTS from one or more cable modems. PHY processing is performed at the CMTS by logic such as that embodied by the BCM3140 device, produced by Broadcom Corporation of Irvine, Calif. Data output from the PHY device is then forwarded to a MAC device (such as the BCM3214 device, also from Broadcom) for subsequent processing, such as fragment reassembly and decryption. A CMTS will typically have several PHY devices and several MAC devices.
In current systems, the number of incoming channels that are mapped to a PHY device is fixed, and the particular PHY devices connected to a MAC device are fixed. Efficiency issues arise when, for example, the PHY devices assigned to a MAC device fail to utilize all the capacity of the MAC. In this case, MAC capacity is wasted. If a second MAC is potentially overloaded, there is no way to balance the load and maintain system-wide throughput, because the mapping of PHY devices to MAC devices is fixed. If PHY devices are hardwired with a MAC device on a single card, the addition of another card may be necessary to handle the extra traffic.
The problem worsens in DOCSIS 2.0 and 3.0 systems. Here, the concept of bonding groups is available. Channel bonding allows a single cable modem to transmit upstream over more than one channel. The channels used by the cable modem are therefore associated, and must be treated as a bonded group at the MAC processing level. A problem arises if a bonding group includes some channels assigned to one MAC device, and other channels assigned to a second MAC device. In this case, neither MAC device sees (i.e., is capable of detecting) all channels of the bonding group. A related problem arises if a bonding group has more channels than a MAC device can normally handle. A group might consist of six channels, for example, while MAC devices are limited to handling four channels each. In this case, no single MAC device could handle all channels of the bonding group.
What is needed, therefore, is a system and method wherein MAC and PHY devices can flexibly and efficiently handle variations in loading brought about by traffic conditions and/or systemic configurations such as channel bonding.